The present invention relates to a video signal transmission apparatus for transmitting a video signal while suppressing a bit rate to a low value by utilizing the characteristics of the video signal, and also to a video system employing such a video signal transmitting apparatus.
Conventionally, various types of video signal transmitting apparatus have been proposed for transmitting video signals while suppressing bit rates to low values in accordance with the processes such as high efficiency coding by utilizing the characteristics of the video signals.
FIG. 1 represents an example of an arrangement of a video system utilizing such a conventional video signal transmission apparatus. In this drawing, reference numerals "1.sub.1 " to "1.sub.K " indicate video cameras, and the video signals (e.g., red, green, and blue color signals) output from these video cameras 1.sub.1 to 1.sub.K are converted into digital video signals. After these digital video signals are processed by bit rate reduction encoders (referred to "BRR encoders" hereinafter) "2.sub.1 " to "2.sub.K " where the bit rates of the digital video signals are lowered, the resulting digital video signals are supplied to a switch circuit 3.
Reference numerals "4.sub.1 " to "4.sub.L " denote VTRs (video tape recorders). The video signals reproduced by these VTRs 4.sub.1 to 4.sub.L are supplied to BRR encoders "5.sub.1 " to "5.sub.L " by which the bit rates of these video signals are lowered in a similar manner to that of the above-described BRR encoders 2.sub.1 to 2.sub.K, whereby the processed video signals are supplied to the switch circuit 3. The video signals in the L-series which are selectively output from the switch circuit 3, are supplied to bit rate reduction decoders (referred to "BRR decoders" hereinafter) "9.sub.1 " to "9.sub.L " by which these video signals are processed in a decoding process complementing the above-described encoding process of the BRR encoders 2.sub.1 to 2.sub.K and 5.sub.1 to 5.sub.K. Thereafter, the resultant video signals are input into the VTRS 4.sub.1 to 4.sub.L as recording signals.
The video signals in M-series selectively output from the switch circuit 3 are supplied to the BRR decoders 6.sub.1 to 6.sub.M, and processed in a manner complementing to that of the above-explained BRR encoders 2.sub.1 to 2.sub.K and 5.sub.1 to 5.sub.L. Thereafter, the processed video signals are supplied to a special effect applying apparatus 7 also known as an effect switcher, or a digital multi-effector (DME).
The video signals in N-series to which either screen switching effects, or 3-dimensional effects are applied by this special effect applying apparatus, are furnished to the BRR encoders 8.sub.1 to 8.sub.N by which the bit rate thereof is lowered in a manner similar to that of the BRR encoders 2.sub.1 to 2.sub.K, 5.sub.1 to 5.sub.L. The resulting video signals are supplied to the switch circuit 3. Then, the video signals in plural series which are selectively output from the switch circuit 3, are derived as the output signals.
After the video signals whose bit rate has been lowered are returned to the original conditions by employing the BRR decoders 6.sub.1 to 6.sub.M in front of the special effect applying apparatus 7 and, the resultant video signal are processed in the specific effect because is that, if the specific effect process (non-linear process) is performed for the video signals whose bit rate has been lowered in the process of high-efficiency coding, the decoding operation would become difficult, resulting in serious deterioration of image qualities.
With the above-described circuit arrangement, both the video signals from the video cameras 1.sub.1 to 1.sub.K, the bit rate of which have been lowered in the BRR encoders 2.sub.1 to 2.sub.K, respectively, and also the video signals in L-series selected by the switch circuit 3 from the video signals that have been processed by the special effect applying apparatus 7 and the bit rates thereof are lowered thereafter by the BRR encoders 8.sub.1 to 8.sub.N, are returned to the original bit rate thereof by the BRR decoders 9.sub.1 to 9.sub.L, and the resulting video signals are input as the recording signals to the VTRs 4.sub.1 to 4.sub.L.
Also, the video signals from the video cameras 1.sub.1 to 1.sub.K whose bit rate has been lowered by the BRR encoders 2.sub.1 to 2.sub.K, the video signals that have been processed in the special effect applying apparatus 7, and whose bit rate have been lowered by the BRR encoders 8.sub.1 to 8.sub.N, and furthermore the video signals in M-series selected by the circuit 3 from the video signals that have been reproduced by the VTRs 4.sub.1 to 4.sub.L and whose bit rate have been lowered by the BRR encoders 5.sub.1 to 5.sub.L, arc returned to the original bit rates thereof by the BRR decoders 6.sub.1 to 6.sub.M, and thereafter are supplied to the special effect applying apparatus 7 for applying the special effect thereto. As a result, the same video signals may pass through the special effect applying apparatus 7 multiple times.
Also, the video signals from the video cameras 1.sub.1 to 1.sub.K whose bit rates have been lowered by the BRR encoders 2.sub.1 to 2.sub.K, the video signals that have been processed by the special effect applying apparatus 7, and whose bit rate has been lowered thereafter by the BRR encoders 8.sub.1 to 8.sub.N, and the video signals in plural series, which have been selected by the switch circuit 3 from the video signals whose bit rates have been lowered by the BRR encoders 5.sub.1 to 5.sub.L, are selectively output as the output signals.
As previously explained, a plurality of BRR decoders 6.sub.1 to 6.sub.M are arranged in front of the special effect applying apparatus 7 and also a plurality of BRR encoders 8.sub.1 to 8.sub.N are arranged following the special effect applying apparatus 7 in the video system shown in FIG. 1. Therefore, the problem is that the cost of these BRR decoders and BRR encoders is high, and thus the cost of the entire video system is high.
After the video signals whose bit rates have been lowered are returned to the original conditions by the BRR decoders 6.sub.1 to 6.sub.M, the resulting video signals are processed by the special effect applying apparatus 7. Because these video signals are processed in the special effect applying apparatus 7 under such conditions that the bit rate thereof is high, this special effect applying apparatus 7 requires a large complicated circuit, resulting in an expensive video system.
In the conventional video system of FIG. 1, when the video signals pass through the specific effect applying apparatus 7 multiple times, these video signals repeatedly pass through the BRR decoder and the BRR encoder. As a result, the quality of the video signals are greatly deteriorated, and therefore it is rather difficult to maintain good image qualities.